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Radio Shack Hardware Manual: Sams Computerfacts - … ·...
Transcript of Radio Shack Hardware Manual: Sams Computerfacts - … ·...
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COMPUTER:RADIO SHACK® TRS-80
MODEL 26-3002
TECHNICAL SERVICE DATA FOR YOUR COMPUTER
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MODEL 26-3002
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PRELIMINARY SERVICE CHECKS
This data provides the user with a time-saving service tool
which is designed for quick isolation and repair of Com-puter malfunctions.
Check all interconnecting cables for good connection and
correct hookup before making service checks.
Disconnect all peripherals except the Monitor from the
Computer to eliminate possible external malfunctions.
Replacement or repair of the power supply board, main
board, keyboard, or connectors may be necessary after the
malfunction has been isolated.
TEST EQUIPMENT AND TOOLS
TEST EQUIPMENT TOOLS
Digital Volt/Ohm Meter
Logic Probe
Frequency Counter
TV Monitor
Low Wattage Soldering Iron
Desoldering Equipment
Switch Cleaner (non spray type)
Phillips Screwdriver
Small Flat Blade Screwdriver
IC Insertion and Removal Tools 14, 16, 24, and 40 pin
Alignment Tools GC Electronics: 9440
REPLACEMENT PARTS AND DESCRIPTION
IDENT PART NO. DESCRIPTIONCR12 ADX1474 Diode, 1N5401
CR13 ADX1474 Diode, 1N5401
F1 AHF1185 Fuse,.7A @ 250V
K1 AR8130 Relay
T1 ATA0856 Power Transformer
U1 AXX3051 IC, MC6809EU2 AMX4584 IC, MC14050BU3 IC, SCM90590PU4 IC, MC6821PU6 IC, SN74LS273NU7 IC, MC6847PU8 IC, MC6821PU9 AMX4585 IC, MC14529BU10 IC, SN74LS783NU11 IC, SN74LS138NU12 IC, MC1372PU13 IC, MC1723CPU14 IC, LM339NU15 IC, MC1741CPU20 IC, RAM MK4116N-3GPthru
U27
U28 IC, SCM90522P
&M*£Ww9r*Howard W. Sams & Co*, Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The listing of any available replacement part herein does not
constitute in any case a recommendation, warranty or guaranty by
Howard W. Sams £ Co. , Inc. , as to the quality and suitability of such
replacement part. The numbers of these parts have been compiled
from information furnished to Howard W. Sams 8 Co., Inc., by the
manufacturers of the particular type of replacement part listed.
Reproduction or use, without express permission, of editorial or pictorial
content, in any manner, is prohibited. No patent liability is assumed with
respect to the use of the information contained herein.
© 1986 Howard W. Sams & Co., Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
Printed in U.S. of America. 85CC14951 DATE 1-86
PRELIMINARY SERVICE CHECtCS (Continued)
TVMONITOR
CASSETTE
POHER L£Fr RJgHTJOYSTICK JOYSTICK
POUER SUPPLYBOARD
INTERCONNECTING DIAGRAM
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© ©KEYBOARD
INTERCONNECTING DIAGRAMRADIO SHACK TRS-80
MODEL 26-3002
PRELIMINARY SERVICE CHECKS (Continued)
U12(4B)(4D)
U10
CLOCK©@@©
U9
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U13
PULSES VOLTAGE
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PIN 11
PULSES
U2? U28 U25 U24 U23 U20 U22 U21
© @ @@IAIN BOARD MAIN BOARD
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PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS
'MATCH THE NUMBERS ON THE INTERCONNECTING DIAGRAM AND PHOTOS WITHTHE NUMBERS ON THE SERVICE CHECKS TO BE PERFORMED.
© COMPUTER DEAD
(A) Check for 18VAC at connectors E1 and E2 and
11.0V at connector E3. If the voltages are miss-
ing check Fuse F1. If Fuse is good check the
windings of Transformer T1 for continuity.
(B) If 1 1 .0V is missing at pin 3 of connector E, checkthe 19VAC winding of Transformer T1 for con-
tinuity and check Diodes CR12 and CR13.
(C) If the voltages are correct at connectors E1, E2and E3, check for 5.0V at TP12. If 5.0V is missing
check the Error Amp IC (U13) by substitution.
(D) If the voltage is not correct at TP12, check the
adjustment of the 5V Adjust Control (R60) (see
"Miscellaneous Adjustments").
(T) MICROPROCESSOR (CPU) OPERATION
(A) Computer is dead. Check for pulses at pins 34
and 35 of the CPU IC (U1). If pulses are missing,
check the Dynamic RAM Controller IC (U10) by
substitution.
(B) If pulses are present at pins 34 and 35 of IC U1,
check for pulses on pins 24 thru 31 of IC U1 while
turning the Computer On. If no pulses appear
check IC U1 by substitution.
(C) If pulses appear on pins 24 thru 31 of IC U1, then
suddenly stop, check RAM IC's (U20 thru U27),
ROM IC (U3) and Expansion ROM IC (U28) by
substitution.
©
©
VIDEO
(A) No video. Check the VDG IC (U7) and Video Mix-
er IC (U12) by substitution.
(B) If IC's U7 and U12 check good, check the adjust-
ment of the Video Level Control (R21) (see Mis-
cellaneous Adjustments).
(C) Dots are missing from the alphanumeric
characters. Check IC U7 by substitution.
(D) Wrong characters appear on the Monitor screen.
Check IC's U6 and U7 by substitution.
COLOR
(A) No color. Check for a frequency of 3.579MHz at
pin 7 of the Dynamic RAM Controller IC (U10). If
the 3.579MHz signal is missing, check IC U10 by
substitution.
(C) Colors are not correct. Check for a frequency of
3.579MHz at pin 7 of IC U10. If the frequency is
not correct, check the adjustment of the Clock
Trimmer (C4) (See "Miscellaneous Ad-justments") and check IC U10 by substitution.
(D) If the frequency is correct at pin 7 of IC U10,
check IC U12 by substitution.
(s) SOUND
©
(A) No sound. Type in and run the following Basic
program:
10 SOUND 200,200: GOTO 10
Check for pulses at pin 3 of the RF Modulator. If
pulses are present, check the adjustment of the
Sound Coil (L4) (See "Miscellaneous Ad-
justments").
(B) If pulses are not present at pin 3 of the RFModulator, check for pulses at pin 14 of the
Analog Multiplexer IC (U9). If pulses are present,
check IC U9 by substitution.
(C) If pulses are not present at pin 14 of IC U9, check
for pulses at pins 4 thru 9 of the PIA IC (U4). If
pulses are present, check the Buffer IC (U2) by
substitution. If pulses are missing check IC U4by substitution.
KEYBOARD
(A) Keyboard is dead. Check the Keyboard Connec-
tor (P6) for good connections.
(B) If the Keyboard Connector (P6) checks good,
check for pulses at pin 11 of ICU11. If pulses are
missing, check IC U11 by substitution.
(C) If pulses are present at pin 11 of IC U11, check
the PIA IC (U8) by substitution.
(D) One key is erratic. Clean the contacts of the bad
key and recheck the operation of the key.
(E) A group of keys do not work. Check the Key-
board Connector (P6) for good connections and
check IC U8 by substitution.
(F) More than one letter appears on the Monitor
screen when a key is pressed. Check for shorted
keys or keys that are stuck down.
(B) If the 3.579MHz signal is good, check the Video
Mixer IC (U12) by substitution.
IV
PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS (Continued)
©
®
CASSETTE
(A) Cassette motor will not run or runs all the time.
Check Relay K1 contacts from pin 1 to pin 3 of
connector P5. Check for continuity while saving
or loading a program from tape if the cassette
motor will not run. Check for a short (contacts
stuck) if the cassette motor runs all the time.
(B) If Relay K1 checks good, check the PIA IC (U4) by
substitution.
(C) Programs can not be saved to tape. Check the
PIA IC (U4) and Buffer IC (U2) by substitution.
(D) Programs can not be loaded from tape. CheckIC's U4 and U14 by substitution.
JOYSTICKS
(A) Joystick does not work. Type in and run the
following program:
10 FORX = 0TO320Y = JOYSTK(X)
30 NEXT X: GOTO 10
While the program is running check for pulses at
pins 19 and 39 of the PIA IC (U8). If pulses are
missing, check IC U8 by substitution.
(B) If pulses are present at pins 19 and 39 of IC U8,check for pulses at pin 11 of the Decoder IC
(U11). If pulses are missing, check IC U11 bysubstitution.
(C) If pulses are present at pin 11 of IC U11, checkfor pulses at pins 4 thru 9 of the PIA IC (U4). If
pulses are missing, check IC U4 by substitution.
(D) If pulses are present at IC U4, check for pulses at
pin 15 of IC U2, If pulses are missing, check IC
U2 by substitution.
(E) If pulses are present at IC U2, check for a varyingvoltage at pi 9 of the Analog Multiplexer IC (U9)
while operating the joystick. If the voltage doesnot vary, check IC U9 by substitution.
(F) If the voltage varies at pin 9 of IC U9, check ICU14 by substitution.
(G) Joystick buttons do not work. Check thejoystick button switches for continuity andcheck the joystick Connectors (P3 and P4) for
good connections.
(H) If the joystick buttons and connectors check —good, check PIA IC (U8) by substitution. q
OSERIAL I/O PORT m
r-
io(A) Serial port does not work. Check the PIA IC (U4) 9
and IC's U14 and U15 by substitution. goto
MISCELLANEOUS ADJUSTMENTS
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5V ADJUST RF MODULATOR
Connect the input of a voltmeter to TP12. Adjust the 5V Ad-
just Control (R60) for a voltage of 5.0V at TP12.
CLOCK ADJUST
Connect the input of a frequency counter to pin 13 of the
Dynamic RAM Controller IC (U10). Adjust the Clock Trim-
mer (C4) for a frequency of 894.886kHz.
Connect the Computer to a TV Monitor and set the TV andChannel Select Switch (S3) to the same channel (channel 3
or 4). Type in and run the following Basic program:
10 SOUND 200,2: GOTO 10
Adjust the Channel Coil (L5) for best picture and sound andadjust the Sound Coil (L4) for best sound with minimumnoise.
PRELIMINARY SERVICE CHECKS (Continued)
U12(4B)(4D)
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© @ @@IAIN BOARD MAIN BOARD
V!
PRELIMINARY SERVICE CHECKS (Continued)
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POWER SUPPLY BOARD
VII
PRELIMINARY SERVICE CHECKS (Continued)
PREVENTATIVE MAINTENANCE
ENVIRONMENT
Computers perform best in a clean, cool area that is below 80 degrees Fahrenheit and free of dust and smoke particles. Eventhough home Computers are not affected by cigarette smoke as much as commercial Computers are affected, it is better tomaintain a smoke-free area around the Computer. Do not block cabinet vents of any of the Computer system; Computer,Monitor, Printer, or other power devices.
ELECTRICAL POWER
Variations in the line voltage can affect the Computer. Try to avoid these fluctuations by using an AC receptacle that is on apower line not used by appliances or other heavy current demand devices. A power-surge protector, power-line conditioner, ornon-interruptable power supply may be needed to cure the problem. Do not switch power On and Off frequently.
KEYBOARD
Liquids spilled into the Keyboard can ruin it. Immediately after a spill occurs, disconnect the Computer power plug from ACpower outlet. Then, if circuitry or contacts are contaminated, disassemble the Keyboard and carefully rinse the Keyboardprinted circuit board with distilled water and let it dry. Use a cotton swab to clean between the keys. Use a non-abrasive con-tact cleaner and lint-free wipers on accessible connectors and contacts.
DISK DRIVES
Clean the read/write heads of the Disk Drives about once a month or after 100 hours usage. Use only an approved head clean-ing kit.
Handle carefully to preserve proper disk head alignment. A sudden bump or jolt to the Disk Drives can knock the disk head outof alignment. If the disk drive must be transported, place an old disk in slot and close door during transport.
Store disks in their protective covers and never touch the disk surface. Observe the disk handling precautions usually foundon the back of disk protective covers.
PRINTERS
Carefully vacuum the Printer regularly. Wipe surface areas clean using a light all-purpose cleaner. Do not oil the machine.The oil will collect abrasive grit and dust. The dust will act as a blanket. This can cause components to overheat and fail.
STATIC ELECTRICITY
Static electricity discharge can affect the Computer. In order to minimize the possibility, use anti-static mats, sprays, toolsand materials, and maintain good humidity in the Computer environment.
MONITOR
Use an isolation transformer with any Monitor that does not come as part of the system since some Monitors use a HOTchassis (chassis connected to one side of the AC line). The face of the Monitor should never be left on for long periods of timeat high brightness level except when pattern is being changed periodically. Use caution when cleaning anti-glare screens, topreserve the glare-reduction feature.
VIII
5j"/Mf COMPUTERFACTS"RADIO SHACK TRS-80
MODEL 26-3002
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PRELIMINARY SERVICE CHECKSENCLOSED
INDEX
SAFETY PRECAUTIONSSee page 18.
Page
Block Diagram 6
Disassembly Instructions 7
General Operating Instructions 7
GridTrace Location Guide 5
IC Pinouts and Terminal Guides 19
Line Definitions 17
Logic Chart 15,16
Miscellaneous Adjustments 7
Parts List 11 thru 14
PagePhotos
Main Board 3,4,21,22
Power Supply Board 20
Safety Precautions 18
Schematics 2,23,24,25
Schematic Notes 17
Test Equipment 8
Troubleshooting 8,9,10
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SAMS* Howard W. Sams & Co., inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The listing of any available replacement part herein does not
constitute in any case a recommendation, warranty or guaranty by
Howard W. Sams & Co., Inc., as to the quality and suitability of such
replacement part. The numbers of these parts have been compiled
from information furnished to Howard W. Sams S Co., Inc., by the
manufacturers of the particular type of replacement part listed.
Reproduction or use, without express permission, of editorial or pictorial
content, in any manner, is prohibited. No patent liability is assumed with
respect to the use of the information contained herein.
© 1986 Howard W. Sams & Co., Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
Printed in U.S. of America. 85CC1 4951 DATE 1 -86
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GridTrace LOCATION GUIDE
C1 C-24 C78 E-8 R24 E-8 U13 N-9C2 H-11 C79 F-8 R25 G-10 U14 F-10C3 J-21 C80 C-11 R26 H-10 U15 D-8C4 L-21 C81 B-10 R27 C-10 U16 L-19C5 F-21 C82 D-12 R28 D-10 U17 0-7C6 F-15 C83 F-24 R29 D-10 U18 N-3C7 0-2 C84 E-15 R30 1-10 U19 N-1C8 P-28 C85 1-23 R31 G-11 U20 0-24C9 L-1 CR1 C-24 R32 G-11 U21 0-27C10 M-13 CR2 K-21 R33 H-11 U22 0-26C11 N-11 CR3 D-24 R34 H-11 U23 0-23CI 2 C-13 CR4 H-11 R35 1-11 U24 0-22CI 3 E-24 CR5 C-10 R36 1-11 U25 0-20C14 P-11 CR6 D-10 R37 E-10 U26 0-19C15 M-6 CR7 D-11 R38 E-10 U27 0-18C16 M-10 CR8 E-17 R39 E-10 U28 F-1
9
C17 L-2 CR9 F-11 R40 D-10 U29 M-14C18 M-1 CR10 F-11 R41 G-11 X1 M-21CI 9 P-9 CR11 1-1 R42 G-11C23 N-23 CR14 0-8 R43 K-21C24 1-13 CR15 N-2 R44 E-18C25 H-13 CR16 1-13 R45 D-22C26 F-15 CR17 N-9 R46 C-23C27 0-16 CR18 G-11 R47 C-13C28 M-1
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El F-1 R48 H-10C29 N-17 E2 G-1 R49 1-10C30 E-18 E3 H-1 R50 C-8C31 0-18 E4 J-1 R51 G-10C32 0-18 E8 L-7 R52 H-10C33 N-20 J1 P-15 R53 G-10C34 H-20 J2 N-15 R54 H-10C35 0-21 J3 P-16 R55 G-10C36 0-9 J4 L-1 7 R56 H-10C37 L-6 J5 K-17 R57 L-20C38 N-2 J6 K-23 R58 0-9C39 0-21 J7 L-5 R59 M-9C40 C-24 K1 D-11 R60 P-12C41 E-15 L2 E-13 R61 0-12C42 F-15 L3 E-13 R62 0-12C43 G-13 L4 D-17 R63 N-11C44 J-23 L5 B-19 R64 N-10C45 0-24 PI G-26 R65 N-10C46 C-24 P2 B-9 R66 M-1
1
C47 N-25 P3 B-7 R67 N-1C48 0-26 P4 B-4 R68 H-20C49 0-26 P5 B-11 R69 H-13C50 E-22 P6 0-14 R71 E-12C51 L-20 01 D-14 R72 1-20C52 H-9 02 K-9 R73 L-2 2C53 M-21 03 L-11 R74 M-23C54 C-3 04 E-11 R75 L-2 3C55 C-3 R1 D-24 R76 M-26C56 C-5 R2 D-24 R77 M-26C57 B-5 R3 E-24 R78 N-26C58 C-8 R4 E-23 R79 N-27C59 E-23 R5 1-20 R80 1-18C60 1-16 R6 E-16 R82 D-22C61 P-17 R7 1-20 R83 J-23C62 0-17 R8 C-13 SI C-23C63 N-19 R9 D-14 S2 C-2C64 0-19 RIO K-20 S3 B-13C65 0-20 R11 K-20 TP12 0-15C66 N-21 R12 K-20 U1 G-23C67 0-22 R13 K-20 U2 K-19C68 0-22 R14 K-20 U3 F-20C69 N-24 R15 K-21 U4 L-1 7C70 0-25 R16 E-13 U5 C-18C71 0-25 R17 L-21 U6 H-1 7C72 N-27 R18 E-15 U7 G-16C73 K-22 R19 E-15 U8 L-1
6
C74 N-15 R20 E-17 U9 H-8C75 M-24 R21 C-14 U10 L-22C76 D-25 R22 1-13 U11 0-16C77 D-24 R23 E-8 U12 F-1
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DISASSEMBLY iNSTRUCTIONS
CABINET REMOVAL MAIN BOARD REMOVAL
Remove seven phiilips screws from cabinet bottom, turn
Computer right side up and lift cabinet top off.
POWER SUPPLY BOARD REMOVAL
Remove three phiilips screws holding power supply board.
Unplug power supply connectors and remove power supply
board.
Remove Power Supply Board and Keyboard. Remove ten
phiilips screws holding Main Board and remove from
cabinet.
KEYBOARD REMOVAL AND DISASSEMBLY
Unplug keyboard from Main Board and remove keyboard
from cabinet. Turn the keyboard upside down and remove21 phiilips screws from the bottom. CAREFULLY lift bot-
tom cover off the keyboard (the keys and contacts are held
in place by the bottom cover and will fall out if the keyboard
is not laying face down.
POWER UP
GENERAL OPERATING INSTRUCTIONS
CASSETTE OPERATION
The Computer will come up in Basic mode when turned Onwith no cartridge in the cartridge slot. If a cartridge is in-
stalled, the Computer will come up running the program in
the cartridge.
RESET
The Computer can be Reset by pressing the Reset Button
(S1) located on the right rear of the cabinet.
BASIC PROGRAMS
A program in Basic can be started by typing RUN and press-
ing the ENTER key. The program can be stopped by press-
ing the BREAK key or the Reset button.
Connect a Cassette Recorder to the Cassette Socket (P5)
on the Computer. The black plug on the cable connects to
the Earphone jack, the large gray plug connects to the Aux-
iliary jack and the small gray plug connects to the RemoteOn/Off jack on the Recorder. To load a program, type
CLOAD, press the Return key, then put the Recorder in Play
mode with the volume turned about halfway up. An S will
appear on the Monitor screen while the Computer searches
for the program. When the Computer finds the program the
letter F will appear on the Monitor screen, then the word OKwill appear after the program has been loaded.
To Save a program to tape, put the Recorder in Recordmode, type CSAVE and press the Return key. The word OKwill appear on the Monitor screen after the program is
Saved.
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MISCELLANEOUS ADJUSTMENTS
5V ADJUST VIDEO LEVEL
Connect the input of a voltmeter to TP12. Adjust the 5V Ad-
just Control (R60) for a voltage of 5.0V at TP12.
CLOCK ADJUST
Connect the input of a frequency counter to pin 13 of the
Dynamic RAM Controller IC (U10). Adjust the Clock Trim-
mer (C4) for a frequency of 894.886kHz.
RF MODULATOR
Connect the Computer to a TV Monitor and set the TV and
Channel Select Switch (S3) to the same channel (channel 3
or 4). Type in and run the following Basic program:
10 SOUND 200,2: GOTO 10
Adjust the Channel Coii (L5) for best picture and sound and
adjust the Sound Coil (L4) for best sound with minimumnoise.
Connect the input of a scope to the emitter of the Video
Amp Transistor (Q1). Set the scope sweep to 20/tSec,
voltage range to 1V, DC input and trigger to negative slope.
Adjust the Video Level Control (R21) for a blanking level of
2.35V (See Figure 1).
2.35V
Figure 1
TEST EQUIPMENTTest Equipment listed by Manufacturer illustrates typical or equivalent equipment used by SAMS' Engineers to obtain
measurements and is compatible with most types used by field service technicians.
TEST EQUIPMENT (COMPUTERFACTS)
Equipment Name8 & K Precision
Equipment No.
Sencore
Equipment No.
SimpsonEquipment No.
OSCILLOSCOPE 1570A,1590A,1596 SC61 454
LOGIC PROBE DP51
LOGIC PULSER DP101
DIGITAL VOM 2830 DVM37,DVM56,SC61 463,467,470,474,467E
ANALOG VOM 277 260-7,160,165,
260-6XL.260-7P,
260-6XLP
ISOLATION TRANSFORMER TR110,1604,1653,1655 PR57
FREQUENCY COUNTER 1803,1805 FC71.SC61 710
COLOR BAR GENERATOR 1211A,1248,1251,1260 CG25.VA62 431
RGB GENERATOR 1260
FUNCTION GENERATOR 3020 420A.420D
HI-VOLTAGE PROBEVOM/DMMAccessory probes
HV-44 HP200 248
00168,00411,00749
TEMPERATURE PROBE TP-28 I R-1 0,00760,00758;
383,389,388
CRT ANALYZER 467,470 CR70
TROUBLESHOOTINGCOMPUTER DEAD
Remove all peripheral equipment that is connected to Com-puter except the Monitor. Turn Computer On. Check the
operation of Computer. If Computer works properly, turn
Computer Off, plug peripherals in one at a time and recheck
operation of Computer until peripheral causing the problem
is found. If Computer does not work with peripherals dis-
connected, check for 5.0V at TP1 2, - 5.0V at TP1 1 and 1 1 .9V
at pin 3 of Voltage Regulator IC (U17). If voltages are miss-
ing, refer to "Power Supply" section. If voltages are cor-
rect, check for pulses on Data pins (24 thru 31) and Addresspins (8 thru 23) of CPU IC (U1). If pulses are missing at any
of the pins, refer to "Microprocessor Operation" section. If
pulses are present, refer to "Video" section.
POWER SUPPLY
Computer is Dead. Check Fuse (F1). If Fuse is bad, checkfor possible shorts to ground at Voltage Regulator IC's
(U17, U18 and U19), Regulator Transistor (Q2) and check for
possible shorted primary or secondary windings onTransformer T1. If Fuse F1 is good, apply 120V AC powerand check for 36V AC from pin 1 to pin 2 and 11.0V.from pin
3 to ground of connector E. If all voltages are missing,
check for open windings on Transformer T1. If 36V AC is
present from pin 1 to pin 2 and 11.0V is missing at pin 3 of
Connector E, check 19V AC winding of Transformer T1 for
possible open circuit and check Diodes CR12 and CR13. If
voltages are correct at Connector E, check for 5.2V at Col-
lector of Regulator Transistor (Q2). If 5.2V is missing, checkvoltages and components associated with pins 2 thru 6 and10 thru 13 of Error Amp IC (U13) and Regulator Transistors
(Q2 and Q3). If voltage reading is not correct at Collector of
Q2, check adjustment of 5V Adjust Control (R60), see"Miscellaneous Adjustments". If voltage is correct at Col-
lector of Transistor Q2, check for - 12.1 V at pin 3 of VoltageRegulator IC (U18). If -12.1V is missing check DiodesCR11 and CR15, Electrolytics C9 and C17 and IC U18. If
- 12.1V is present at pin 3 of IC U18, check for -5.0V at pin
3 of IC U19. If -5.0V is missing, check Resistor R67, Elec-
trolytic C18 and IC U19. If -5.0V is present at pin 3 of IC
U19, check for 11.9V at pin 3 of IC U17. If 11.9V is missing,
check Diodes CR11 and CR14, Electrolytic C7 and IC U17.
MICROPROCESSOR (CPU) OPERATION
Computer is dead, power supply checks good. Use a scopeto check data lines (pins 24 thru 31 of IC U1) for activity. If
there is no activity check operation of reset circuit by
checking logic reading at pin 37 of CPU IC (U1). The reading
should be Low when the Computer is turned On then im-
mediately go High. The logic reading should also be Lowwhenever Reset switch (S1) is pressed. If logic reading is
not correct at pin 37 of IC U1 when Computer is turned On,
check Electrolytic C1, Diodes CR1, CR2 and CR3 and
Resistor R2. If Power On reset works but Reset Switch (S1)
does not work, check Switch (S1), Capacitor C40, Diodes
CR1 and CR3 and Resistor R1. If reset circuit is operating
properly, check for 894.886kHz clock pulses at pins 34 and
35 of IC U1. If clock pulses are missing, check waveform at
pin 5 of the Dynamic Ram Controller IC (U10). If waveform is
missing, check Crystal X1, Capacitor C51, Trimmer C4,
Resistor R43 and IC U10. If waveform is present at pin 5 of
IC U10, check waveforms at pins 13 and 14 of IC U10. If
waveforms are missing at pins 13 and 14 of IC U10, check IC
U10 and Capacitors C73 and C75.
If clock pulses check good at pins 34 and 35 of IC U1 , check
for a logic High at pins 2, 3, 4 and 40 of IC U1. If logic
reading is not correct at any pin, check IC's and com-ponents that are connected to defective pin.
To check for address lines that may be stuck logic High or
Low, connect a Jumper from pin 40 of IC U1 to ground. All
address lines (pins 8 thru 23 of IC U1) should check logic
open. If any address line checks logic Low or High, check
IC's that are connected to defective line. Grounding pin 40
of IC U1 also causes pins 24, 25, 27 and 28 of IC U1 to go
TROUBLESHOOTING (Continued)
logic Low and pins 26, 29, 30 and 31 to go logic High. If any
readings are not correct on pins 24 thru 31 of IC U1, check
IC's connected to pin with incorrect reading.
Computer will come up properly when turned On, if PIA IC
(U8), Analog Multiplexer IC (U9), IC U14 and Expansion ROMIC (U28) are removed. Turn Computer Off and reinstall IC's
one at a time and recheck opertion of Computer until defec-
tive IC is located.
If pulses appear on data pins (24 thru 31) of IC U1 whenComputer is turned On then suddenly stop, check RAM IC's
(U20 thru U27), ROM IC (U3) and Expansion ROM IC (U28).
VIDEO
Colors are not correct. Check for a frequency of
3.57954MHz at pin 7 of Dynmaic RAM Controller IC (U10). If
frequency is not correct, check adjustment of the
14.31818MHz Clock Trimmer (C4), see "Miscellaneous Ad-justments". If correct frequency cannot be obtained by ad-
justing Trimmer C4, check Crystal X1, Capacitor C51,
Resistor R43 and IC U10. If frequency is correct at pin 7 of
IC U10, check waveforms at pins 5 and 7 of Video Mixer IC
(U12). If waveforms are missing or incorrect, check VDG IC
(U7). If waveforms are present, check IC U12.
SOUND
No sound. Type in and run following Basic program. Theprogram produces a continuous tone from Monitor speaker.
No video. Check waveform at emitter of Video Amp Tran-
sistor (Q1). If waveform is present check adjustment of
Video Level Control (R21) and check for 6.1V at pin 2 of RFModulator. If Control R21 is adjusted properly and 6.1V is
present at pin 2 of RF Modulator, check RF Modulator. If
6.1V is missing at pin 2 of RF Modulator, check Resistor
R45. If R45 is good refer to the "Power Supply" section of
this Troubleshooting guide.
If waveform is missing at emitter of Transistor Q1, checkwaveform at pin 12 of Video Mixer IC (U12). If waveform is
present at pin 12 of IC U12, check voltages and componentsassociated with Transistor Q1. If waveform is missing at
pin 12 of IC U12, check waveform at pin 9 of IC U12. If
waveform is present at pin 9 of IC U12, check IC U12.
If waveform is missing at pin 9 of IC U12 check VDG IC (U7).
Dots are missing from alphanumeric characters. Check IC
U7.
Wrong characters appear on Monitor screen. Check for
pulses at pins 2, 5, 6, 9, 12, 15, 16 and 19 of Latch IC (U6). If
pulses are missing at any pins, check IC U6. If pulses are
present at IC U6, check IC U7.
VIDEO GRAPHICS
One or more Graphics modes do not work. Type in and run
following program:
10FORX = 0TO420 PMODE X: SCREEN X
30 NEXT X: GOTO 10
The program continually switches between five Graphics
modes that are available. While program is running, check
for pulses at pins 27, 29, 30 and 35 of the VDG IC (U7). If
pulses are missing, check PIA IC (U4) and Dynamic RAMController IC (U10). If pulses are present, check IC U7.
COLOR
No Color. Check 3.58MHz waveform at pin 33 of VDG IC
(U7). If waveform is missing, check Dynamic RAM Con-
troller IC (U10). If waveform is present at pin 33 of IC U7,
check waveforms at pins 8 and 10 of Video Mixer IC (U12).
The waveform at pin 10 of IC U12 should look like the
waveform at pin 8 with an amplitude of .3V peak to peak. If
waveform is present at pin 8 and missing at pin 10 of IC U12,
check Capacitor C42 and Resistor R18. If waveform is miss-
ing at pin 8 of IC U12, check IC U12.
10 SOUND 200,200: GOTO 10
While program is running, check for pulses at pins 3, 5, 7, 9,
1
1
and 14 of Buffer IC (U2). If pulses are missing, check PIA
IC(U4). If pulses are present at pins 3, 5, 7, 9, 11 and 14 of IC
U2, check for pulses at pins 2, 4, 6, 10, 12 and 15 of IC U2. If
pulses are missing, check IC U2. If pulses are present at
pins 2, 4, 6, 10, 12 and 15 of IC U2, check for pulses at pin 14
of Analog Multiplexer IC (U9). If pulses are missing at pin 14
of IC U9, check Capacitor C52 and Resistors R10 thru R15and R72. If pulses are present at pin 14 of IC U9, check for
pulses at pin 10 of IC U9. If pulses are missing at pin 10 of
IC U9, check for a logic Low at pins 6 and 7 of IC U9. If pin 6
or 7 of IC U9 do not read logic Low, check PIA IC (U8). If
pins 6 and 7 of IC U9 are correct, check IC U9. If pulses are
present at pin 10 of IC U9 check adjustment of Sound Coil
(L4) on RF Modulator, see "Miscellaneous Adjustments".
KEYBOARD
Keyboard dead. Check keyboard Connector (P6) for goodconnections. If connector checks good, check for pulses at
pin 11 of Decoder IC (U11). If pulses are missing, check IC
U11. If pulses are present at pin 11 of IC U11, check PIA IC
(U8).
One key is erratic or dead. Check bad key for continuity. If
key checks bad, clean key contacts and recheck key.
A group of keys do not work. Check keyboard Connector
(P6) for good connections. If connector checks good, check
ICU8.
More than one letter appears on Monitor screen when a key
is pressed. Check for shorted keys or keys that are stuck
down.
CASSETTE
Cassette motor does not turn Off. Check for 0V at pin 39 of
PIA IC (U4). If the voltage is not correct, check IC U4. If
voltage is correct at pin 39 of IC U4, check for 5.0V at collec-
tor of Relay Driver Transistor (Q4). If voltage is not correct,
check Transistor Q4. If voltage is correct at collector of
Transistor Q4, check for possible sticking contacts in Relay
K1 and check Capacitor C80 and Zener Diodes CR9 and
CR10 for possible shorts.
Cassette motor will not turn On. Type in and run the follow-
ing Basic program. The program turns On Cassette Motor.
10 POKE 65313,60
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TROUBLESHOOTING (Continued)
After running program, check for .9V at pin 38 of PIA IC (U4).
If voltage is not correct at pin 38 of IC 114, check IC U4. If
voltage is correct at pin 38 of IC U4, check for .1 V at collec-
tor of Relay Driver Transistor (Q4). If voltage is not correct,check Transistor Q4, Diode CR7 and Relay K1.
Programs can not be saved on cassette. Type in and run thefollowing Basic program which continuously saves itself to
cassette.
10 CSAVE: GOTO 10
While program is running, check for pulses at pins 5 thru 9of IC U4. If pulses are missing at pins 5 thru 9 of IC U4,check IC U4. If pulses are present at pins 5 thru 9 of IC U4,check for pulses at pins 4, 6, 10, 12 and 15 of Buffer IC (U2).
If pulses are missing at pin 4, 6, 10, 12 or 15 of IC U2, checkIC U2. If pulses are present at IC U2, check for a 1 V peak to
peak waveform at pin 5 of Connector P5. If waveform is
missing at pin 5 of Connector P5, check Capacitors C52 andC82 and Resistors R41 and R42.
Programs cannot be loaded from cassette. Inject a 4V peakto peak 1000Hz square wave at pin 4 of cassette Connector(P5). Check for pulses at pin 13 of IC U14. If pulses aremissing, check voltages and components associated withpins 10, 11 and 13 of IC U14. If pulses are present at pin 13of IC U14, check PIA IC (U4).
JOYSTICK
Joysticks do not work. Type in and run the following Basicprogram to check operation of joysticks.
10 FORX = 0TO320N(X) = JOYSTK(X)
30 NEXT X40 PRINT "RIGHT JOYSTICK HORIZONTAL = ";N(0)
50 PRINT "RIGHT JOYSTICK VERTICAL = ";N(1)
60 PRINT "LEFT JOYSTICK HORIZONTAL = ";N(2)
70 PRINT "LEFT JOYSTICK VERTICAL = ";N(3)
80PRINT "RIGHT BUTTON = ";(PEEK(65280) AND 1)
90 PRINT "LEFT BUTTON = "; PEEK(65280) AND 2)
100 FOR t = 1 TO 100:NEXTT:CLS:GOTO 10
The numbers that appear on Monitor screen for joystickhorizontal and vertical positions should vary from to 63while the joystick is being operated. The numbers that ap-pear for the joystick buttons should change to the numberOwhenever the button is pressed.
Check the joystick Connectors (P3 and P4) for good connec-tions. While program is running, check for pulses at pins 19and 39 of PIA IC (U8). If pulses are missing at pin 19 or 39 of
IC U8, check IC U8. If pulses are present at pin 19 and 39 of
IC U8, check for pulses at pin 10 of Decoder IC (U11). If
pulses are missing at pin 10 of IC U11, check IC U11. if
pulses are present at pin 10 of IC U11, check for pulses at
pins 4 thru 9 of PIA IC (U4). If pulses are missing at pins 4thru 9 of IC U4, check IC U4. If pulses are present at pins 4thru 9 of IC U4, check for pulses at pins 2, 4, 6, 10, 12 and 15of Buffer IC (U2). If pulses are missing at pin 2, 4, 6, 10, 12,or 15 of IC U2, check IC U2. If pulses are present at IC U2^check voltage at pin 9 of Analog Multiplexer IC (U9) whileoperating joystick. The voltage should vary between 0V and5V. If voltage does not vary at pin 9 of IC U9, checkCapacitors C54, C55, C78 and C79 and IC U9. If voltagereadings are correct at pin 9 of IC U9, check for pulses at pin
14 of IC U14. If pulses are missing at pin 14 of IC U14, checkIC U14. If pulses are present at pin 14 of IC U14, checkvoltage at pin 8 of IC U14 while operating the joystick. Thevoltage should vary between OV and 5V. If voltage readingis not correct, check Capacitor C52 and Resistors R10 thru
R15 and R72.
Joystick buttons do not work. If right joystick button doesnot work, check for a logic Low at pin 2 of PIA IC (U8) whilepressing right joystick button. If reading is correct, checkIC U8. If reading is not correct, check Coil L2, check pins 3and 4 of Connector P3 for good connections and check joy-
stick button for continuity. If left joystick button does notwork, check for a logic Low at pin 3 of IC U8 while pressingleft joystick button. If reading is correct, check IC U8. If
reading is not correct, check Coii L3, check pins 3 and 4 ofConnector P4 for good connections and check joystick but-
ton for continuity.
SERIAL I/O PORT
Serial I/O port (Connector P2} does not work. Disconnectany equipment connected to serial port and connect ajumper from pin 4 to pins 1 and 2 of Connector P2. Type in
.and run the following Basic program.
10 POKE 65312,0
20 PRINT "0 OUTPUT ON U4.PIN 3"
30 PRINT "PIN 40=";(PEEK(85313) AND 128)
40X = PEEK(65312)
50 PRINT "PIN 10 = ";(PEEK{65314) AND 1)
60 POKE 65312,255
70 PRINT "1 OUTPUT ON U4.P1N 3"
80 PRINT "PIN 40 = ";(PEEK(65313) AND 128)
90X = PEEK(65312)
100 PRINT "PIN 10=";{PEEK(65314) AND 1)
110FORT = 1 TO50:NEXTT:CLS:GOTO10
The program toggles the serial output pin (pin 3) of PIA IC
(U4) back and forth from 1 to and reads the Carrier Detect
pin (pin 40) and RS232 IN pin (pin 10) of IC U4. The programcontinuously prints results on Monitor screen. When a is
output on pin 3, pin 40 should read 128 and pin 10 shouldread 0. When a 1 is output on pin 3, pin 40 should read andpin 10 should read 1. If readings are correct on Monitorscreen, problem may be in equipment that was connectedto port or in software used to operate the port.
If readings are not correct on Monitor screen, check for
pulses at pin 3 of IC U4 while program is running. If pulsesare missing on pin 3 of IC U4, check IC U4, If pulses are
present at pin 3 of IC U4, use a scope to check for pulsesthat swing from - 10V to + 10V at pin 6 and IC U15. If thepulses are missing or are not correct at pin 6 of IC U15check voltages and components associated with pins 1 thru
4 and 6 of IC U15 and check IC U15. if pulses are present at
pin 6 of IC U15, check for pulses at pins 1 and 2 of IC U14. If
pulses are missing at pin 1 or 2 of IC U14 check voltages
and components associated with pins 1 , 2, 4, 5, 6 and 7 of IC
U14 and check iC U14. If pulses are present at pins 1 and 2
of IC U14, check iC U4.
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PARTS LIST AND DESCRIPTION (Continyed)
When ordering parts, state Model, Part Number, and Description
ELECTROLYTIC CAPACITORS CAPACITORS
ITEM
No.RATING MFGR.
PART No.
C17thruC19
1 uF 50V ACC105QJTP
ITEM
No.RATING MFGR.
PART No.
C4 9pF-35pF AC-4926
RESISTORS (Power and Special)
ITEM
No.RATING
REPLACEMENT DATA
MFGR.PART No.
NTEPART No.
WORKMANPART No.
R10R11
R12R13R14R15R75
10K \% 1/4W Carbon Film20K \% 1/4W Carbon Film40. 2K M 1/4W Carbon Film80. 6K \$ 1/4W Carbon Film162K \% 1/4W Carbon Film324K 1% 1/4W Carbon FilmRes i stor Network ( 1
)
AN0281BEEAN0306BEEAN0597BEEAN0359BEEAN0385BEEAN0408BEEARX0220
(1) Contains four (4ea) 33 ohms.
COILS (RF-SF)
ITEM
No.FUNCTION
MFGR.PART No.
L2L3
RF Choke (3.3uH)RF Choke (3.3uH)
ACA8059ACA8059
TRANSFORMER (Power)
ITEM
No.
RATINGREPLACEMENT DATA
MFGR.PART No.
NOTESPRI. SEC. 1 SEC. 2
T1 120V AC S
130mA AC18V AC $
50mA AC18V AC i
160mA ACATA0856993-0433 (1)
SEC. 3 SEC, 4 SEC. 5
19V AC a
600mA DC
30
3 2o oS w">go« ^O -JO 31
<POSo
(1 ) Number on unit.
CONTROLS (All waffages 1/2 watt, or less, unless listed)
ITEMNO.
FUNCTION RESISTANCEMFGR.
PART NO.NOTES
R21
R60Video Level+5V Adjust
5001000
AP7156AP0835
13
PARTS LIST AND DESCRIPTION (Continued)
When ordering parts, state Model, Part Number, and Description
FUSE DEVICES
ITEM
NO.DESCRIPTION
MFGR.PART NO.
NOTES
DEVICE HOLDER
F1 .7A % 250VFast-Acting
AHF1185 AFI176
MISCELLANEOUSITEM
PART NAME MFGR.NOTES
No. PART No.
K1 Relay AR81 30 Cassette EnableR73 Ferrite Bead 2643021801R74 Ferrite Bead 2643021801R75 Ferrite Bead 264000301R76 Ferrite Bead 264000301R77 Ferrite Bead 264000301SI Switch S0852 ResetS2 Switch S0851 PowerS3 Switch S9142 Channel SelectXI Crystal AMX2797 14.31818MHz
Keyboard AXX0206 Comp 1 eteKeyboard Cab 1 e AW2589Power Cord AW2587
CABINETS & CABINET PARTS (When ordering specify model, chassis & color)
ITEM PART No.
Cabinet TopCabinet BottomCartridge Door
AZ5844AZ5845ADA0337
WIRING DATAShielded Hook-up Wire Use BELDEN No. 8401 or 8421 (Single-Conductor)
8208 (Two-Conductor)General-use Unshielded Hook-up Wire Use BELDEN No. 8529 (Solid) Available in 13 Colors
8522 (Stranded) Available in 13 Colors300-Ohm Input Lead Use BELDEN No. 822575-Ohm Input Lead Use BELDEN No. 8241
14
LOGIC CHART
PIN PIN PIN PIN PIN PINNO. Ul NO. Ul NO U2 U3 NO. U3 NO. U4 NO. U4
1 L 21 P 1 H P 21 P 1 L 21 P2 H 22 P 2 L P 22 P 2 L 22 H3 P 23 P 3 L P 23 P 3 H 23 H4 H 24 P 4 L P 24 H 4 L 24 H
5 P 25 P 5 L P 5 L 25 P6 L 26 P 6 L P 6 L 26 P7 H 27 P 7 L P 7 L 27 P8 P 28 P 8 L P 8 L 28 P
9 P 29 P 9 L P 9 L 29 P10 P 30 P 10 L P 10 H 30 P11 P 31 P 11 I P 11 * 31 P12 P 32 P 12 L L 12 H 32 P
13 P 33 P 13 * P 13 L 33 P14 P 34 P 14 L P 14 L 34 H15 P 35 P 15 L P 15 L 35 P36 P 36 P 16 * P 16 L 36 P
1? P 37 H 17 P 17 L 37 H18 P 38 P 18 P 18 H 38 H19 P 39 L 19 P 19 L 39 L20 P 40 H 20 P
1
20 H 40 H
PIN PIN PIN PINNO. U6 U7 NO. U7 NO. U8 NO. U8
1 H L 21 P 1 L 21 P2 P P 22 P 2 H 22 H3 P P 23 P 3 H 23 P4 P P 24 P 4 H 24 H
5 P P 25 P 5 H 25 P6 P P 26 P 6 H 26 P7 P P 27 L 7 H 27 P8 P P 28 8 H 28 P
9 P 29 L 9 H 29 P10 L 30 L 10 P 30 P11 P 11 31 L 11 P 31 P12 P P 32 P 12 P 32 P
13 P P 33 13 P 33 P14 P P 34 P 14 P 34 H35 P P 35 I 15 P 35 P16 P P 36 P 16 P 36 P
1? P H 37 P 17 P 37 P18 P P 38 P 18 P 38 P19 P P 39 L 19 L 39 L20 H P 40 P 20 H 40 P
15
LOGIC CHART (Continued)
PIN PIN PIN PINNO. U10 NO. U10 WO U11 NO. U16 U20 U21 U22 U23 U24
1 P 21 P 1 P 1 P L L L L L2 P 22 P 2 P 2 P P P P P P3 P 23 P 3 P 3 P P P P P P4 P 24 P 4 P 4 P P P P P P
5 P 25 P 5 L 5 P P P P P P6 P 26 P 6 H 6 P P P P P P7 P 27 P 7 P 7 P P P P P P8 P 28 P 8 L 8 P H H H H H
9 P 29 P 9 H 9 P H H H H H10 P 30 P 10 H 10 L P P P P P11 P 31 P 11 P 11 P P P P P P12 P 32 P 12 H 12 P P P P P P
13 P 33 P 13 P 13 P P P P P P14 P 34 P 14 P 14 P P P P P P15 P 35 P 15 P 15 P P P P P P16 P 36 P 16 H 16 P L L L L L
17 P 37 P 17 P18 P 38 P 18 P19 P 39 P 19 P20 L 40 H 20 H
PIN PIN PINNO. U25 U26 U27 U28 NO U28 NO U29
1 L L L P 21 P 1 H2 P P P P 22 P 2 L3 P P P P 23 P 3 L4 P P P P 24 H 4 H
5 P P P P 5 L6 P P P P 6 L7 P P P P 7 L8 H H H P 8 P
9 H H H P 9 P10 P P P P 10 P11 P P P P 11 #
12 P P P L 12 *
13 P P P P 13 L14 P P P P 14 H15 P P P P16 L L L P
17 P18 P19 P20 P
16
SCHEMATIC NOTES
-*- Circuitry not used in some versions-— Circuitry used in some versions
e See parts list
4r Groundrrtr, ChaSSIS
<j Common tie point
Waveforms and voltages taken from ground, unless noted
otherwise.
Voltages, Waveforms and Logic probe readings taken with
computer turned On, no keys pressed, unless otherwise
noted.
Waveforms taken with triggered scope and Sweep/Time
switch in Calibrate position, scope input set for DCcoupling on reference voltage waveforms. Switch to ACinput to view waveforms after DC reference is measured
when necessary. Each waveform is 7 cm. width with DCreference voltage given at the bottom line of each wave-
form.
Time in /isec. per cm, given with p-p reading at the end of
each waveform.
Item numbers in rectangles appear in the alignment/ad-
justment instructions.
Supply voltages maintained as shown at input.
Voltages measured with digital meter, no signal.
Controls adjusted for normal operation.
Terminal identification may not be found on unit.
Capacitors are 50 volts or less, 5% unless noted.
Electrolytic capacitors are 50 volts or less, 20% unless
noted.
Resistors are V2W or less, 5% unless noted.
Value in( ) used in some versions.
Measurements with switching as shown, unless noted.
Logic Probe Display
L = LowH = High
P = Pulse
*=Open (No light On)
LINE DEFINITIONS
A0 THRU A15 Address
CART Cartridge Presence Interrupt
CAS Column Address Strobe
CASS MOT Cassette Motor
CASS OUT Cassette Output
CASSDIN Cassette Data Input
CD Status Interrupt Input (RS232C)
CSN Cartridge Sound
CTS Cartridge Select Signal
DO THRU D7 Data
DAO Display Address Ero
E Clock, 1/16 Master Clock, CPU RAM Addressing
EN1 ROM Enable
EN2 ROM Expansion Enable
FIRQ . Fast Interrupt Request, Does Not Maintain Registers
FS Field Sync
H1 Chip Select, PIA CSO and CS1
HALT Halt CPU Input
HS Horizontal Sync
IRQ Interrupt Request
MAO THRU MA6 Memory Address
MDO THRU MD7 Memory Data
NMI Nonmaskable Interrupt
PIAO Peripheral Interface Adapter Ero
PIA1 Peripheral Interface Adapter OneQ Clock, 1/16 Master Clock,
Leads E Clock by Ninety Degrees
R/W Read/Write
RAS Row Address Strobe
RESET Reset
RS232 RS232 Interface System
RS232 IN RS232 Interface System Input
SCS Spare Cartridge Signal, Selects Address Space
SEL 1, SEL 2 PIA Select Outputs, Joy Sticks or SoundSLENB Select Enable, Disables Internal Selection,
Utilities Unused MemorySND Sound Source in Cartridge
VDG CLK Video Display Generator Clock
WE Write Enable
3D>O50)I>O
wO —1O 33
00o
17
SAFETY PRECAUTIONS
1. Use an isolation transformer for servicing.
2. Maintain AC line voltage at rated input.
3. Remove AC power from the Computer before servicing or installing electrostatically sensitive devices. Examples oftypical ES devices are integrated circuits and semiconductor 'chip" components.
4. Use extreme caution when handling the printed circuit boards. Some semiconductor devices can be damaged easily bystatic electricity. Drain off any electrostatic charge on your body by touching a known earth ground. Wear a commercial-ly available discharging wrist strap device. This should be removed prior to applying power to the unit under test.
5. Use a grounded-tip, low voltage soldering iron.
6. Use an Isolation (times 10) probe on scope.
7. Do not remove or install board, floppy disk drives, printers, or other peripherals with power On.
8. Do not use freon-propelled sprays. These can generate electrical charges sufficient to damage semiconductor devices.
9. The Computer cabinet is equipped with vents to prevent heat build-up. Never block, cover, or obstruct these vents.
10. Instructions should be given, especially to children, that objects should not be dropped or pushed into the vents of thecabinet. This could cause shock or equipment damage.
11"
waLTsTr086 the C°mpUter ,0 Wa,er
'!f exP°sed t0 water
.tum the unit off. Do not place the Computer near possible
12. Never leave the Computer unattended or plugged into the AC outlet for long periods of time. Remove AC plug from ACoutlet during lightning storms.
13. Never use liquids or aerosols directly on the Computer. Spray on cloth and then apply to the Computer cabinet. Makesure the Computer is disconnected from the AC power line.
18
SC PSNOUTS & TERMINAL GUIDE?
SN74LS138NMC1372P IDENT
SELECT -<
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RF TANK
SF TANK
RF MODULATOR
OUTPUT
8ND
COLORSINPUT
COLOR REP
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COLOR AINPUT
CHROMINANCE
INPUT
LUMINANCE
INPUT
CHROMA NODUUTOROUTPUT
IDENT
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=116
=115
314313312
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31039
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U3,U28TOP VIEW
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TOP VIEW
MC14529B
SN741S244N
MC1723CP
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CURRENT FREQUENCY
LIMIT COMPENSATION
CURRENTV*
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DAS DAS
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DA9 DAI
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DA11 DA12
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SN74LS783N
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GENERATORTOP VIEW
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A10 A12
AS A13
AB AM
OSC IN A15
OSC OUT Z7
VCLK Z6
DAO 75
HS 24
IS Z3
CAS Z2
RASO Z1
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A1 A7
A2 AS
A3 AS
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MC680SEP
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PA0 CA2
PA1 1R0A
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PAS RSO
PA4 RSI
PAS RESET
PAS DO
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PBO D2
PB1 03
PS2 D4
PBS 05
PB4 OS
P65 D7
W6 E
PB7 CS1
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